that's a great way to do it for sure, and similar to what SLOVFR and I did back in 08 when we rode from Cali up to Washington state, but this is a first proposed big trip without a couple shorter ones thrown in to get used to it, or that's what I was thinking he said anyway... It's a lot of slab time if you are not used to it... I just did a little over 600 miles in a day coming back from Mexico last month and it was hella tough for the last 200 miles slabbing. It gets old fast. I could definitely tell that my reaction times were slower and I'd catch myself spacing out. You can get away with that a little in a car, but it's not generally advisable on a bike. IMO, the trip the OP mentions should be done in 2 days each way.
Trick is to build up with many short trips. correct-the stopping and resting is important, take longer, rest often. Last year I took Red Rocket (98) from St. Louis to Denver (860mi) -16 hrs out via 2 lane finishing last 2 hrs. in a dry lighting storm in eastern CO-scariest part of any trip I've taken over 30 years. Trip back 14 hrs via I-70, boring. I think, tank bag (drinks & camera), saddle bags work well and any type of seat cushion helps. Standing upright on the pegs for a few minutes every so often doesn't help mileage but does allow blood back to butt. Oh, by the way I'm in my 60s